How is bell's palsy diagnosed?

Depends on the Cause: Bell's palsy itself can be diagnosed just with a history and physical exam. However, the cause of bell's palsy can be idiopathic (unknown cause) or range from infection to a tumor. Therefore your physician may want to run additional tests to find the cause of bell's palsy.

Exam and tests: Bell's palsy is facial weakness or paralysis that is thought to be caused by a viral infection. It is diagnosed by the medical history and on physical exam. Many times additional testing such as a cat or MRI scan will be used to rule out other causes such a a tumor growth.